Application-added Variables

Application-added Variables

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Geometry Expressions does not require you to specify your model in every detail.  The underlying geometry engine automatically fills in any variables youve left unspecified.

For example, the following drawing (typical of many geometry problems) constrains the shape of the triangle but not its location: 

 

Asking for the coordinates of points A and B, then, requires the system to add variables for the location of point A and the direction of line AB:

 

 

By default, Geometry Expressions creates the variables u0 and v0 for the x and y coordinates of point A, and θ0 for the direction of the line AB. It associates numeric values with these variables based on the location of the pertinent object on the drawings coordinate system.

Geometry Expressions cannot always calculate sample values so easily. When a variable is used in more than one place, or when it is involved in a complicated expression, the application solves equations to come up with appropriate sample values. However, whatever values it assigns, you can always set your own values directly in the Variables panel (discussed in “Controlling Variables”).